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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The largest organelle is usually the nucleus • The nucleus is separated from the cytoplasm by the nuclear envelope • The nucleus is the cellular control center – It contains the DNA that directs the cell’s activities 4.6 The nucleus is the cell’s genetic control center ORGANELLES OF THE ENDOMEMBRANE SYSTEM
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The largest organelle is usually the nucleus
• The nucleus is separated from the cytoplasm by the nuclear envelope
• The nucleus is the cellular control center
– It contains the DNA that directs the cell’s activities
4.6 The nucleus is the cell’s genetic control center
ORGANELLES OF THE ENDOMEMBRANE SYSTEM
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 4.6
Chromatin
Nucleolus
Pore
NUCLEUS
Two membranesof nuclearenvelope
ROUGHENDOPLASMICRETICULUM
Ribosomes
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Ribosomes-non-membrane bound organelles
• Ribosomes are free or attached to the endomembranous system of endoplamic reticulum
• They are where proteins are built.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The endomembrane system is a collection of membranous organelles
– These organelles manufacture and distribute cell products
– The endomembrane system divides the cell into compartments
– Endoplasmic reticulum (ER) is part of the endomembrane system
4.7 Overview: Many cell organelles are related through the endomembrane system
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• The rough ER manufactures membranes• Ribosomes on its surface produce
proteins
4.8 Rough endoplasmic reticulum makes membrane and proteins
1 2
3
4Transport vesiclebuds off
Ribosome
Sugarchain
Glycoprotein
Secretory(glyco-) proteininside transportvesicle
ROUGH ER
PolypeptideFigure 4.8
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• Smooth ER synthesizes lipids
• In some cells, it regulates carbohydrate metabolism and breaks down toxins and drugs
4.9 Smooth endoplasmic reticulum has a variety of functions
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SMOOTH ER
ROUGHER
Nuclearenvelope
Ribosomes
SMOOTH ER ROUGH ER
Figure 4.9
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• The Golgi apparatus consists of stacks of membranous sacs
– These receive and modify ER products, then send them on to other organelles or to the cell membrane
4.10 The Golgi apparatus finishes, sorts, and ships cell products
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• The Golgi apparatus
Golgiapparatus
“Receiving” side ofGolgi apparatus
Transportvesiclefrom ER
Newvesicleforming
Transport vesiclefrom the Golgi
Golgi apparatus
“Shipping”side of Golgiapparatus Figure 4.10
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• Lysosomes are sacs of digestive enzymes budded off the Golgi
4.11 Lysosomes digest the cell’s food and wastes
LYSOSOME
Nucleus
Figure 4.11A
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• Lysosomal enzymes
– digest food
– destroy bacteria
– recycle damaged organelles
– function in embryonic development in animals
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Figure 4.11B
Rough ER
Transport vesicle(containing inactivehydrolytic enzymes)
Golgiapparatus
Plasmamembrane
LYSOSOMES
“Food”
Engulfmentof particle
Foodvacuole
Digestion
Lysosomeengulfingdamagedorganelle
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• Lysosomal storage diseases are hereditary
– They interfere with other cellular functions
– Examples: Pompe’s disease, Tay-Sachs disease
4.12 Connection: Abnormal lysosomes can cause fatal diseases
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• Plant cells contain a large central vacuole
– The vacuole has lysosomal and storage functions
4.13 Vacuoles function in the general maintenance of the cell
Centralvacuole
Nucleus
Figure 4.13A
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• Protists may have contractile vacuoles
Figure 4.13B
Nucleus
Contractilevacuoles
– These pump out excess water
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• The various organelles of the endomembrane system are interconnected structurally and functionally
4.14 A review of the endomembrane system
Transport vesiclefrom ER
Rough ER
Transport vesiclefrom Golgi
Plasmamembrane
Vacuole
LysosomeGolgiapparatusNuclear
envelopeSmooth ER
Nucleus
Figure 4.14
